Fast thermal dumping for batteries

ABSTRACT

A cooling system includes a fluid delivery system configured to bring a working liquid (such as water) into thermal contact with a battery where it vaporizes into an exhaust gas, and an exhaust system configured to vent the exhaust gas.

If an Application Data Sheet (ADS) has been filed on the filing date ofthis application, it is incorporated by reference herein. Anyapplications claimed on the ADS for priority under 35 U.S.C. §§ 119,120, 121, or 365(c), and any and all parent, grandparent,great-grandparent, etc. applications of such applications, are alsoincorporated by reference, including any priority claims made in thoseapplications and any material incorporated by reference, to the extentsuch subject matter is not inconsistent herewith.

SUMMARY

In one aspect, a system for cooling thermal runaway in a batter includesa fluid delivery system configured to transport a working liquid (e.g.,water, a CFC, an HFC, an HCFC, a BCFC, or a mixture thereof) intothermal contact with the battery and further configured to permit theworking liquid to vaporize to form an exhaust gas, and an exhaust systemconfigured to vent the exhaust gas. The system may include a storagetank for the working liquid, and may be configured to work without aconnection to an external source of working liquid. The system mayinclude a structure configured to route the working liquid through thebattery interior, for example multiple channels that bring workingliquid through a plurality of locations within the battery. These may beconfigured to cool the battery at different cooling rates in differentlocations, for example separately controlling the cooling rate of eachcell of a multi-cell battery. The fluid delivery system may include apump, a valve, or a pressurization source (e.g., a source pressurized bya portion of the exhaust gas). The system may further include triggeringcircuitry configured to activate the cooling system in response to abattery condition (e.g., temperature, current, rate of change oftemperature, acceleration, acceleration history, speed, speed history,internal pressure of the battery, or structural integrity of thebattery), and optionally a memory configured to store a record of thebattery condition or a record of the cooling system activation. Thesystem may include a heat transfer structure (e.g., including a heatpipe, a coolant flow conduit, or a thermal conductor) configured totransport heat from the interior of the battery to an external heatexchanger, where the fluid delivery system is configured to route theworking liquid into thermal contact with the external heat exchanger.The system may include triggering circuitry configured to activate thecooling system in response to an external command, or flow ratecircuitry configured to control a flow rate of the working liquid withinthe fluid delivery system in response to a battery condition (e.g.,battery temperature profile). The system may be configured to deliverworking liquid to different cells of the battery at different rates.

In another aspect, a method of cooling a battery includes bringing aworking liquid (e.g., water, a CFC, an HFC, an HCFC, a BCFC, or amixture thereof) into thermal contact with the battery, allowing theworking liquid to vaporize to form an exhaust gas, and venting theexhaust gas. The method may include storing the working liquid theworking liquid in a storage tank, and bringing it from the tank withoutan existing connection to an external liquid supply. The method mayinclude routing the working liquid through the battery interior, forexample via multiple channels that bring working liquid to a pluralityof locations within the battery. These may be configured to cool thebattery at different cooling rates in different locations, for exampleseparately controlling the cooling rate of each cell of a multi-cellbattery. The method may include pumping the working liquid. The methodmay further include activating the cooling system in response to abattery condition (e.g., temperature, current, rate of change oftemperature, acceleration, acceleration history, speed, speed history,internal pressure of the battery, or structural integrity of thebattery), and optionally storing a record of the battery condition or arecord of the cooling system activation in a memory. The method mayinclude transporting heat via a heat transfer structure (e.g., a heatpipe, a coolant flow conduit, or a thermal conductor) from the interiorof the battery to an external heat exchanger, and placing the workingliquid into thermal contact with the external heat exchanger. The methodmay include activating the cooling system in response to an externalcommand, or adjusting a flow rate of the working liquid within the fluiddelivery system in response to a battery condition (e.g., batterytemperature profile). The method may include delivering working liquidto different cells of the battery at different rates.

In still another aspect, a system for cooling a battery includes meansfor bringing a working liquid (e.g., water, a CFC, an HFC, an HCFC, aBCFC, or a mixture thereof) into thermal contact with the battery, meansfor allowing the working liquid to vaporize to form an exhaust gas, andmeans for venting the exhaust gas. The system may include a storage tankthat stores the working liquid, and means for bringing it from the tankwithout an existing connection to an external liquid supply. The systemmay include means for routing the working liquid through the batteryinterior, for example via multiple channels that bring working liquid toa plurality of locations within the battery. These may be configured tocool the battery at different cooling rates in different locations, forexample separately controlling the cooling rate of each cell of amulti-cell battery. The means for bringing the working liquid intothermal contact with at least a portion of the battery may include apump, a valve, or a pressurization source. The system may furtherinclude means for activating the cooling system in response to a batterycondition (e.g., temperature, current, rate of change of temperature,acceleration, acceleration history, speed, speed history, internalpressure of the battery, or structural integrity of the battery), andoptionally means for storing a record of the battery condition or arecord of the cooling system activation in a memory. The system mayinclude means for transporting heat via a heat transfer structure (e.g.,a heat pipe, a coolant flow conduit, or a thermal conductor) from theinterior of the battery to an external heat exchanger, and means forplacing the working liquid into thermal contact with the external heatexchanger. The system may include means for activating the coolingsystem in response to an external command, or means for adjusting a flowrate of the working liquid within the fluid delivery system in responseto a battery condition (e.g., battery temperature profile). The systemmay include means for delivering working liquid to different cells ofthe battery at different rates.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a battery cooling system.

FIG. 2 is a flow chart of a method of operating the battery coolingsystem of FIG. 1.

FIG. 3 is a detail of a battery having separate flow control indifferent cells.

FIG. 4 is a detail of a battery having valves to control routing ofexhaust gas.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here.

The term “circulated,” as it is used herein, includes flowing a fluidthrough a pipe, channel, or conduit, or through an indeterminate pathsuch as through an open-cell foam, either once or multiple times. Theterm “recirculated,” as it is used herein, includes circulating a fluidin a configuration in which it passes through the same portion of anapparatus more than once.

FIG. 1 is a schematic drawing illustrating a cooling system for abattery 100, such as an auto battery. Battery 100 includes multiplecells 102, each with a positive and negative terminal as shown. Cells102 are wired in parallel and connected to positive and negative batteryterminals 104 in a conventional manner. A fluid delivery system includesreservoir 106, pump 108, heat exchanger pipes 110, and exhaust 112.Reservoir 106 holds a working liquid 114. Any convenient working liquidthat may be circulated through the battery at its working temperatureand that may be vaporized as described below may be used. It is expectedthat water will represent a good working liquid in many embodiments,since it has a relatively high heat of vaporization and is innocuouswhen vented to the atmosphere, but in some embodiments, more exoticworking liquids may be appropriate, such as chlorofluorocarbons (CFCs,e.g., FREON™), hydrofluorocarbons (HFCs), hydrofluorochlorocarbons(HCFCs), bromochlorofluorocarbons (BCFCs), or mixtures of any of thepreceding compounds, which may, for example, be azeotropic mixtures.

Heat exchanger pipes 110 are provided that allow working liquid 114 fromreservoir 106 to be circulated through the battery, either by freeconvection or assisted by one or more pumps 108. (One pump isillustrated in FIG. 1, but in other embodiments, pumps 108 may beprovided throughout the system, which may be jointly or separatelycontrolled, as further discussed below in connection with FIG. 3.Alternatively, instead of a pump, the system may harness pressuregenerated by vaporization of working fluid 114 or the energy of acatastrophic event precipitating rapid cooling, as further discussedbelow.) In the embodiment shown in FIG. 1, the system includes definedpipes in thermal communication with the battery cells 102, but in otherembodiments, fluid may be circulated around or even through the cells inany convenient configuration. For example, cells 102 may be embedded inan open-cell foam through which the working liquid 114 circulates, orthere are may be perforations in cells 102 that are designed to permitworking fluid 114 to exchange heat with cells 102 without unacceptablydegrading the electrical performance of the cells. In some embodiments,solid heat pipes or similar structures (not shown) conduct heat out ofthe cells to the heat exchanger pipes 110. The illustrated heatexchanger pipes 110 are connected to exhaust 112 that allows vaporizedworking liquid to be vented, for example to the atmosphere or to asealed balloon or the like (not shown) where it can be subsequentlyharvested for reuse.

FIG. 2 is a flow chart illustrating steps of one method of using thecooling system illustrated in FIG. 1. In normal operation, workingliquid 114 circulates 202 through battery 100 to cool it, either throughfree convection or assisted by pump 108. However, upon experiencing aprecipitating event 204, system 100 shifts to an irreversible coolingmode designed to cool the battery as fast as possible, before thermalrunaway can occur. In some embodiments, precipitating events may includetemperature exceeding a threshold, rate of temperature change exceedinga threshold, rapid acceleration of the system (e.g., an impact),internal pressure of the battery, compromise of the integrity of one ormore cells 102, or a received command such as a wireless command. In theembodiment shown in FIG. 1, working liquid 114 is pumped through thesystem by pump(s) 108 to cool the battery 206, and is allowed tovaporize 208 to absorb as much heat as possible via evaporative cooling,and is vented to the atmosphere through exhaust 112.

FIG. 3 is a schematic showing the interior of a battery equipped toindividually control the cooling rate for each cell. Each cell 302 hasan associated heat exchanger pipe 310, each with its own pump 308. Theschematic illustration shows each heat exchanger pipe 310 as a looparound cell 302, but it will be understood that the path of each pipe310 may vary from this configuration, and should be designed toefficiently remove heat from cell 302. Thermocouple 304 is positioned tomeasure the temperature of cell 302, and to provide a feedback signal topump 308. The speed of pump 308 is controlled relative to thetemperature measured by thermocouple 304 so that cell 302 is cooled at acontrolled rate, which can be independently controlled for each cell302. For example, more cooling may be needed for cells in the center ofthe battery than for cells at the periphery.

Thermocouple 304 and pump 308 may also be connected to circuitry formeasuring and recording the temperature and cooling rate of the battery.In some embodiments, such a record may include time-stamping orplace-stamping (e.g., via GPS), so that the performance of the batterycan be reconstructed, for example for forensic purposes after anaccident.

In other embodiments, rather than directly routing the working liquidthrough the battery, the battery may include thermal conductors (heatpipes) configured to transport heat to a heat exchanger. In someembodiments, a single or a few heat pipes may serve the whole battery,which is others, individual heat pipes may be provided for each cell orother region of the battery interior. In embodiments in which heat pipesare provided to transport heat to a heat exchanger, the working liquidis brought into thermal contact with the heat pipes, which in someembodiments may be outside of the main battery compartment. Those ofskill in the art will recognize that this design may facilitate theconstruction of batteries that need not be able to tolerate workingliquid in the battery interior, but that this advantage must be balancedagainst possible inefficiencies in transporting heat to the workingliquid (instead of transporting the working liquid to the heat source).

Pressures generated by vaporization of a working liquid in a battery canbe quite high if the fluid is not adequately vented. Plumbing in thebattery should generally be designed with an eye to managing pressuresto avoid rupturing a heat exchanger pipe within the battery, although insome embodiments, planned rupture may be used to improve heat transferwithin the battery. However, such pressures can also be leveraged toincrease fluid flow, in some embodiments even to the point where pump108 can be omitted from the system. In some embodiments, liquidrecirculates around the battery (with or without a pump), until thecooling system is activated (for example, by a substantial temperatureexcursion within the battery, or by a detected rapid decelerationindicative of an impact).

FIG. 4 shows an exhaust system that uses internal pressure to reroutethe path of the exhaust gas. Working liquid 414 is stored in reservoir406 and circulated through battery 416, absorbing heat from the batteryand vaporizing to form exhaust gas. Exhaust port 418 for the vaporizedexhaust gas leads to a chamber 420 having two one-way, pressureactivated, valves. Recirculation valve 422 opens at a first pressure P₁,thereby allowing pressurization of the reservoir 406. If the pressurereaches a greater pressure P₂, exhaust valve 424 opens, allowing excessexhaust gas to be vented through exhaust pipe 412.

While the novel batteries presented herein may be used in stationaryapplications, they are particularly well-suited for use in vehicles orother devices that move independently (e.g., robots or autonomousvehicles). In such embodiments, the vehicle or other device typicallycarries a tank of working liquid that may be vented in the case of abattery failure. For example, currently used electric vehicle batteriesusually store about 15-60 kW-h of electrochemical energy. Water absorbsabout 2.3 kJ/g when vaporized, so it would require about 22-87 kg ofwater to be vaporized to dissipate all of the electrochemical energy inthe battery (neglecting energy used to heat the water to the boilingpoint and any possible parasitic losses), a reasonable amount to carrywith the battery in a dedicated storage tank or the like (22 kg of wateroccupies less than a cubic foot of space). (Dichlorodifluoromethane(FREON-12) is much less efficient with a latent heat of vaporization of0.17 kJ/g, but may nevertheless be preferable in some embodiments.)Those of skill in the art will understand that these numbers areestimates used to demonstrate feasibility of the concept and are notintended to be limiting. In some embodiments, slower cooling orincomplete cooling may be tolerable, in which case less working liquidmay be carried. In other embodiments, speed of cooling may be paramount,in which case pumping must be faster and thermal transfer to the workingliquid made as efficient as possible to optimize performance.

Various embodiments of electrochemical devices and methods have beendescribed herein. In general, features that have been described inconnection with one particular embodiment may be used in otherembodiments, unless context dictates otherwise. For example, theindividual cell cooling described in connection with FIG. 3 may beemployed in the devices described in connection with FIG. 4, or with anyof the embodiments described herein. For the sake of brevity,descriptions of such features have not been repeated, but will beunderstood to be included in the different aspects and embodimentsdescribed herein.

It will be understood that, in general, terms used herein, andespecially in the appended claims, are generally intended as “open”terms (e.g., the term “including” should be interpreted as “includingbut not limited to,” the term “having” should be interpreted as “havingat least,” the term “includes” should be interpreted as “includes but isnot limited to,” etc.). It will be further understood that if a specificnumber of an introduced claim recitation is intended, such an intentwill be explicitly recited in the claim, and in the absence of suchrecitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage ofintroductory phrases such as “at least one” or “one or more” tointroduce claim recitations. However, the use of such phrases should notbe construed to imply that the introduction of a claim recitation by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a cell” should typically be interpreted to mean “at leastone cell”); the same holds true for the use of definite articles used tointroduce claim recitations. In addition, even if a specific number ofan introduced claim recitation is explicitly recited, it will berecognized that such recitation should typically be interpreted to meanat least the recited number (e.g., the bare recitation of “two heatpipes,” or “a plurality of heat pipes,” without other modifiers,typically means at least two heat pipes). Furthermore, in thoseinstances where a phrase such as “at least one of A, B, and C,” “atleast one of A, B, or C,” or “an [item] selected from the groupconsisting of A, B, and C,” is used, in general such a construction isintended to be disjunctive (e.g., any of these phrases would include butnot be limited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, or A, B, and C together,and may further include more than one of A, B, or C, such as A₁, A₂, andC together, A, B₁, B₂, C₁, and C₂ together, or B₁ and B₂ together). Itwill be further understood that virtually any disjunctive word or phrasepresenting two or more alternative terms, whether in the description,claims, or drawings, should be understood to contemplate thepossibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

What is claimed is: 1-55. (canceled)
 56. A system for cooling a battery,comprising: means for bringing a working liquid into thermal contactwith at least a portion of the battery, wherein the working liquidincludes a liquid chosen from water, a chlorofluorocarbon, ahydrofluorocarbon, a hydrofluorochlorocarbon, and abromochlorofluorocarbon; means for allowing heat from the battery tovaporize the working liquid; and means for venting the vaporized workingliquid.
 57. (canceled)
 58. The system of claim 56, wherein the workingliquid further includes a mixture of liquids chosen from achlorofluorocarbon, a hydrofluorocarbon, a hydrofluorochlorocarbon, anda bromochlorofluorocarbon.
 59. The system of claim 56, wherein the meansfor bringing the working liquid into thermal contact with at least aportion of the battery includes means for bringing the working liquidfrom a storage tank without an existing connection to an external liquidsupply.
 60. The system of claim 56, wherein the means for bringing theworking liquid into thermal contact with at least a portion of thebattery includes means for routing working liquid through the batteryinterior.
 61. The system of claim 60, wherein the means for bringing theworking liquid into thermal contact with at least a portion of thebattery includes means for routing the working liquid through aplurality of locations within the battery.
 62. The system of claim 61,wherein the means for bringing the working liquid into thermal contactwith at least a portion of the battery includes means for coolingdifferent portions of the battery at different cooling rates.
 63. Thesystem of claim 62, wherein the battery includes a plurality of cells,and wherein the means for bringing the working liquid into thermalcontact with at least a portion of the battery includes means forseparately cooling each cell of the battery.
 64. The system of claim 56,wherein the means for bringing the working liquid into thermal contactwith at least a portion of the battery includes a pump.
 65. The systemof claim 56, wherein the means for bringing the working liquid intothermal contact with at least a portion of the battery includes a valve.66. The system of claim 56, wherein the means for bringing the workingliquid into thermal contact with at least a portion of the batteryincludes a pressurization source.
 67. The system of claim 66, whereinthe pressurization source includes at least a portion of the exhaustgas.
 68. The system of claim 56, wherein the means for bringing theworking liquid into thermal contact with at least a portion of thebattery includes means for activating the cooling system in response toa battery condition.
 69. The system of claim 68, wherein the batterycondition is temperature.
 70. The system of claim 68, wherein thebattery condition is current.
 71. The system of claim 68, wherein thebattery condition is rate of change of temperature.
 72. The system ofclaim 68, wherein the battery condition is acceleration, accelerationhistory, speed, or speed history of the battery.
 73. The system of claim68, wherein the battery condition is internal pressure of the battery.74. The system of claim 68, wherein the battery condition is structuralintegrity of the battery.
 75. The system of claim 68, further comprisingmeans for storing a record of the battery condition in a memory.
 76. Thesystem of claim 68, further comprising means for storing a record of thecooling system activation in a memory.
 77. The system of claim 56,further comprising means for transporting heat from the interior of thebattery to an external heat exchanger, wherein the means for bringingthe working liquid into thermal contact with at least a portion of thebattery includes means for bringing the working liquid into thermalcontact with the external heat exchanger.
 78. The system of claim 77,wherein the means for transporting heat from the interior of the batteryto an external heat exchanger include a heat pipe.
 79. The system ofclaim 77, wherein the means for transporting heat from the interior ofthe battery to an external heat exchanger include a coolant flowconduit.
 80. The system of claim 77, wherein the means for transportingheat from the interior of the battery to an external heat exchangerinclude a thermal conductor.
 81. The system of claim 56, wherein themeans for bringing the working liquid into thermal contact with at leasta portion of the battery includes means for activating the coolingsystem in response to an external command.
 82. The system of claim 56,further comprising means for responding to a battery condition byadjusting a flow rate of working liquid delivered to the battery. 83.The system of claim 82, wherein the means for responding to a batterycondition by adjusting a flow rate of working liquid delivered to thebattery include means for adjusting the flow rate of working liquid inresponse to a battery temperature profile.
 84. The system of claim 56,wherein the battery includes a plurality of cells, and wherein the meansfor bringing the working liquid into thermal contact with at least aportion of the battery includes means for delivering liquid toindividual cells at different rates.